my main source of dosing is kalk, but I supplement with 2 part now. I dose kalk using a reactor that stirs the mixture and a litermeter 3. I also use the litermeter 3 to dose the 2 part mixture using remote pumps. Not the cheapest option, but the litermeter doses more often than other options and I bought it before I had an apex. I am pretty sure I could replace it with dosing pumps, but I already have the litermeter and trust it 100%. The only issue I ever had was when it got dropped into saltwater during an upgrade, but that was obviously my fault. I've had to replace the tubing before as well, but since I bought it used, I learned my lesson and bought 2 replacements lines. Its got a run timer to remind you to do maintenance as well. All around a good product.